Abstract: Thickener is a crucial component in 3D printing materials. However, commonly used thickeners are predominantly organic matter, leading to a reduction in the mechanical performance of gypsum. In order to solve this issue, attapulgite clay and hydroxypropyl methylcellulose ether were compared to test their effects on the workability performance, mechanical performance, and printability of gypsum 3D printing materials. The results show that, attapulgite clay reduces the fluidity of gypsum 3D printing materials and increases dynamic yield stress, similar to hydroxypropyl methyl cellulose ether. The flexural and compressive strength of the material decreases first and then increases as the attapulgite clay content increases, while the flexural and compressive strength of the hydroxypropyl methylcellulose ether group shows a declining trend. In the actual 3D printing process, the volume stability and open time results of attapulgite clay groups are similar to those of the hydroxypropyl methylcellulose ether groups, but the actual printing strength is more than 23% higher than that of the hydroxypropyl methylcellulose ether groups. Hydroxypropyl methylcellulose ether achieves viscosity enhancement by water absorption and molecular entanglement, whereas attapulgite clay, with its abundant pore structure, thickens the slurry by adsorbing water molecules and gypsum particles through hydrogen bonding and Van der Waals forces.

Key words: high-strength gypsum, 3D printing, inorganic thickener, attapulgite clay, workability performance, printability